使用C#来连接并操作Access数据库，洪哥把它封装成了一个类。
这个类主要有如下一些功能：连接数据库、打开数据库连接、关闭数据库连接、执行SQL语句、ExecuteScalar（可返回数字、字符串等不同类型的值）、获取DataTable等。
using System.Collections.Generic;
using System.Text;
using System.Data.OleDb;
using System.Data;
public class DbAccess
{
public static string ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + CConfig.DbPath;
public static string ErrorMessage = "";
private static OleDbConnection objConnection = new OleDbConnection();
private static OleDbCommand objCommand = new OleDbCommand();
/// <summary>
/// Open Database
/// </summary>
/// <returns>return True while success, otherwise False</returns>
private static bool OpenConn()
{
objConnection.ConnectionString = ConnectionString;
try
{
objConnection.Open();
return true;
}
catch (Exception ex)
{
ErrorMessage = ex.ToString();
return false;
}
}
/// <summary>
/// Close Database
/// </summary>
private static void CloseConn()
{
if (objConnection.State == System.Data.ConnectionState.Open)
{
try
{
objConnection.Close();
}
catch { }
}
}
/// <summary>
/// ExecuteNonQuery
/// </summary>
/// <param name="strSql">input, SQL statement</param>
/// <param name="intCount">output, Lines affected while executing the SQL</param>
/// <returns>True/success, False/fail</returns>
public static bool ExecuteNonQuery(string strSql, out int intCount)
{
intCount = -1;
objCommand.CommandType = System.Data.CommandType.Text;
objCommand.CommandText = strSql;
if (OpenConn())
{
objCommand.Connection = objConnection;
intCount = objCommand.ExecuteNonQuery();
CloseConn();
return true;
}
else
{
return false;
}
}
/// <summary>
/// Get Row 1 Column 1, Integer
/// </summary>
/// <param name="strSql"></param>
/// <param name="i"></param>
/// <returns></returns>
public static bool ExecuteScalar(string strSql, out int i)
{
i = -1;
objCommand.CommandType = System.Data.CommandType.Text;
objCommand.CommandText = strSql;
if (OpenConn())
{
objCommand.Connection = objConnection;
i = (int)objCommand.ExecuteScalar();
CloseConn();
return true;
}
else
{
return false;
}
}
/// <summary>
/// Get Row 1 Column 1, String
/// </summary>
/// <param name="strSql"></param>
/// <param name="str"></param>
/// <returns></returns>
public static bool ExecuteScalar(string strSql, out string str)
{
str = null;
objCommand.CommandType = System.Data.CommandType.Text;
objCommand.CommandText = strSql;
if (OpenConn())
{
objCommand.Connection = objConnection;
Object o = objCommand.ExecuteScalar();
if (o is DBNull)
{
str = "";
}
else
{
str = o.ToString();
}
CloseConn();
return true;
}
else
{
return false;
}
}
/// <summary>
/// Get DataTable
/// </summary>
/// <param name="sql"></param>
/// <returns></returns>
public static DataTable GetDataSet(string sql)
{
DataSet dataset = new DataSet();
objCommand.CommandType = CommandType.Text;
objCommand.CommandText = sql;
if (OpenConn())
{
objCommand.Connection = objConnection;
OleDbDataAdapter da = new OleDbDataAdapter(objCommand);
da.Fill(dataset);
CloseConn();
}
return dataset.Tables[0];
}
}
ExecuteScalarExecuteScalar